SearchWiki has been replaced with a simple feature that lets you star search results. Click on a star next to a search results and you'll see it in a "starred items" OneBox at the top of the page. Another side effect is that the starred search results are added to Google Bookmarks, so you can quickly find them later. The "starred items" OneBox shows the most relevant bookmarks that match your query and it's the easiest way to search Google Bookmarks.
Those who used SearchWiki to remove search results or to add comments won't lose their changes. "If you previously removed a result, it will remain hidden whenever you do the same search in the future. These hidden results will be listed in a "removed results" section at the bottom of the page," explains Google. There's also a SearchWiki page that lists all your notes.
Even if I didn't like SearchWiki at the beginning, I ended up using this feature a lot. Adding web pages to search results pages and improving the snippets with custom annotations were a great way to refind web pages.